Explanation: The cyaniding process is an expensive process of surface hardening of steels which is applied to produce automobile parts. It requires lesser time and lower temperatures than carburizing. It also lowers warping and distortion while increasing the corrosion and wear resistance.

Explanation: Carbonitriding is a surface hardening process that involves the diffusion of nitrogen and carbon into the steel. Carbonitriding may also be called as gas-cyaniding or dry-cyaniding.

Explanation: The carbonitriding process is carried out in a gas atmosphere furnace using a carburizing gas such as propane or methane mixed with ammonia. The workpiece is heated to 850oC in the mixture of gases for 2-10 hours followed by quenching and tempering.

Explanation: The carbonitriding process is carried out in a gas atmosphere furnace using a carburizing gas.The workpiece is heated to 850oC in the mixture of gases for 2-10 hours. This is followed by quenching to increase hardness, then by tempering at 180oC for reducing the brittleness.

Explanation: Of all the diffusion surface hardening methods, carburizing provides the highest cast depth of 1.38 mm. This is followed by carbonitriding, nitriding, and cyaniding at 0.5 mm, 0.38 mm, and 0.25 mm correspondingly.

Explanation: Carbonitriding process of surface hardening results in a case depth of 0.5 mm and a hardness after heat treatment of HRC 65. Interestingly, carburizing and cyaniding also result in equal hardness after heat treatment.

Explanation: Nitriding process provides an extreme hardness of the surface and a case depth of 0.38 mm. It is typically used for valve guides and seatings, and for gears.

Explanation: Nitralloy steels are commonly used in nitriding process. These steels are hardened by oil quenching from 900oC and tempered at 600-700oCbefore nitriding.